This invention relates to a magneto-resistance effect device used for a magneto-resistance effect head for detecting a playback signal by the magneto-resistance effect and that is advantageously applied to, for example, a hard disc device, or a magnetic sensor for detecting geomagnetism by the magneto-resistance effect.
In a magnetic recording/reproducing device, such as a hard disc device, a higher recording density is required for further improving surface recording density of a magnetic recording medium. Thus, for realizing of high recording density, a magneto-resistance effect type thin-film magnetic head (MR head) employing a magneto-resistance effect device of high magnetic field sensitivity, has come to be used.
The magneto-resistance effect device 100 illustrated in FIG. 1, used for an MR head which has achieved high recording density, has a substantially rectangular magneto-resistance effect layer 101 and a pair of electrodes 102A, 102B arranged on both longitudinal ends of the magneto-resistance effect layer 101. In the magneto-resistance effect device 100, a magneto-resistance effect stabilizing layer for magnetically stabilizing the magneto-resistance effect layer 101 or a non-magnetic layer is layered in the direction of the film thickness of the magneto-resistance effect layer. When reproducing a magnetic field signal recorded on the magnetic recording medium, an area sandwiched between the paired electrodes 102A, 102B operates as a magnetically sensitive area R to which a pre-set constant amount of the sense current is supplied from the paired electrodes 102A, 102B.
If an external magnetic field, such as a magnetic field signal, is impressed across the magneto-resistance effect device 100 described above, the resistance value of the magneto-resistance effect layer 101 is changed. In the magneto-resistance effect device 100, the sense current is supplied to the magneto-resistance effect layer 101 for specifying the changes in resistance in terms of changes in voltage. In the MR head employing this magneto-resistance effect device 100, the changes in voltage of the sense current are detected for reproducing the signal 1f of the magnetic recording medium. This MR head is classified as either a so-called transverse MR head supplying the sense current in a substantially parallel direction to the magnetic recording medium or a so-called longitudinal MR head supplying the sense current in a substantially perpendicular direction to the magnetic recording medium.
The transverse MR head is arranged so that the longitudinal direction of the magneto-resistance effect device is substantially parallel to the magnetic recording medium. In the transverse MR head, the magneto-resistance effect layer of the magneto-resistance effect device is magnetized in a direction substantially parallel to the magnetic recording medium, and the signal magnetic field is impressed from a direction substantially perpendicular to the direction of magnetization of the magneto-resistance effect layer.
In the longitudinal MR head, the output remains constant under constant sense current density condition, even if the track width is reduced. Thus, if the track width is reduced, a higher output is realized. Moreover, since the electrically conducive material arranged on a sliding surface of the longitudinal MR head along which slides the magnetic recording medium can be of the same potential, high resistance against electrostatic destruction is achieved. In addition, with the longitudinal MR head, the sense current magnetic field is produced if the sense current is supplied. Since the sense current magnetic field stabilizes the magneto-resistance effect device along the easy axis, no magnetic domain stabilizing layer is required.
If, with the above-described transverse and longitudinal MR heads, the sense current is supplied to the magneto-resistance effect device, the sense current magnetic field is generated from the sense current. This sense current magnetic field is an annular magnetic field centered about the maximum sense current density distribution.
Also, the magneto-resistance effect device is arranged so that the position of the magneto-resistance effect layer is not coincident with the center of the sense current magnetic field, because the magneto-resistance effect stabilizing layer or the non-magnetic layer is layered on the magneto-resistance effect layer. Thus the annular sense current magnetic field is applied to the magneto-resistance effect layer.
In the transverse MR head, since the direction of the sense current magnetic field is substantially perpendicular to the direction of magnetization of the magneto-resistance effect layer, the sense current magnetic field operates as a bias magnetic field for the magneto-resistance effect layer. Therefore, with the transverse MR head, the playback sensitivity can be improved by utilizing the sense current magnetic field as the bias magnetic field.
On the other hand, with the longitudinal MR head, employing the above-described magneto-resistance effect device, the direction of the sense current magnetic field generated in the magneto-resistance effect layer is substantially parallel to the direction of magnetization of the magneto-resistance effect layer. With the longitudinal MR head, the direction of magnetization of the magneto-resistance effect layer is oriented along the direction of easy axis. By this sense current magnetic field, the magnetic field of the same direction as the anisotropic magnetic field of the magneto-resistance effect layer, referred to herein as an effective anisotropic magnetic field, is increased. That is, the sense current magnetic field is generated in the direction of the track width of the magneto-resistance effect device for increasing the effective anisotropic magnetic field. This effective anisotropic magnetic field is impressed on the magneto-resistance effect layer for increasing the magnetization of the magneto-resistance effect layer oriented along the direction of easy axis.
Thus, with the magneto-resistance effect device used in the longitudinal MR head, the direction of magnetization is not liable to be changed even on impression of a signal magnetic field from the magnetic recording medium, thus deteriorating the magneto-resistance effect characteristics. That is, the longitudinal MR head has a defect that the magneto-resistance effect device is lowered in sensitivity by the sense current magnetic field.
It may also be envisaged to increase the amount of the sense current for increasing the sensitivity of the magneto-resistance effect device used in the longitudinal MR head. However, if the amount of the sense current s increased, the sense current magnetic field is increased simultaneously, so that, in the magneto-resistance effect device, the effective anisotropic magnetic field is increased. Therefore, with this magneto-resistance effect device, the magneto-resistance effect device cannot be improved in sensitivity by increasing the amount of the sense current, such that the above problem cannot be solved.